The height of a bed apparatus is normally predetermined. That is, the height of the bed apparatus is set to a predetermined height which allows convenient use for a user having an average physical construction.
For example, a user lies or sits on such a bed apparatus every day. The user repeatedly gets on/off the bed apparatus every time he lies or sits on the bed apparatus.
Various users such as tall, short, young, old, and healthy persons and a patient use such bed apparatuses.
Of these users, for example, a short person who tries to sit on a bed apparatus whose mattress surface is set high, finds it difficult to do so.
It is, similarly, too difficult for an old person or patient to get on/off a bed apparatus whose mattress surface is set high. The optimal height of a bed apparatus varies depending on users. Strong demand has arisen for developing a bed apparatus capable of changing the height depending on the need of a user.
To solve this problem, a hospital bed apparatus used in a hospital is available. In a height-adjustable hospital bed apparatus, a complicated link mechanism mounted on the lower surface of a base is actuated by a power source to vertically move the base.
A conventional bed apparatus capable of changing its height by means of a power source has a very complicated structure. For this reason, this bed apparatus is too expensive.